Gastrointestinal stromal tumors (GISTs) are soft-tissue sarcomas that can be located in any part of the digestive system. Their most common sites are the stomach and small intestine.

GISTs start in specialized nerve cells located in the walls of your digestive system. These cells are part of the autonomic nervous system. A specific change in the DNA of one of these cells, which control such digestive processes as movement of food through the intestines, gives rise to a GIST.

Small GISTs may cause no symptoms, and they may grow so slowly that they have no serious effects. People with larger GISTs usually seek medical attention when they vomit blood or pass blood in their stool due to rapid bleeding from the tumor.

Other possible GIST symptoms include:

• Anemia, caused by a slow-bleeding tumor
• Abdominal pain
• A growth you can feel in your abdomen
• Nausea
• Vomiting
• Loss of appetite
• Weight loss
• Difficulty swallowing